On Wed, 14 Mar 2018 10:39:43 -0700, tabbypurr wrote:

On Wednesday, 14 March 2018 14:47:42 UTC, NY wrote:
tabbypurr wrote in message
...
On Wednesday, 14 March 2018 09:54:42 UTC, whisky-dave wrote:

But it is true the problem with LED lightbulbs is that they do get
very hot at the base as that's where the SMPS are but the heat can
be transfered to the actual LEDs which don;t like being hot.
The life of the lamps might well be UP TO 15K hours but they are
very liklely to fail long before that due to temperature as the 15K
hours refers to an LED used within the specs and even then it
doesn't mean it will last 15,000 hours.

The heat comes from the LED, it doesn't get transferred to the LED.

Ah, is the heat mainly from the LEDs rather than the PSU?

almost entirely

And that's also the case with CFLs (in this case, the compact
fluorescent tube).

The cheaper LED lamps use a lossless (literally!) capacitor dropper
usually with a low value resistor in series to limit inrush current. It's
this resistor that introduces a modicum of loss into the ballast circuit
- maybe 5 or 10 percent of the energy dissipated by the LEDs themselves.

The more sophisticated switch mode ballast circuits probably account for
less than 5% of the waste heat energy in an LED lamp so in either case,
just as for the CFL, the majority of the waste heat comes from the LED
string itself.

The good thing about LED lamps is their potential to achieve efficacies
five times greater than the best CFLs ever could. Cree Lighting
demonstrated a laboratory 303 LPW LED lamp some four years ago which,
contrary to the head of Cree's marketing division's claim of "it takes 18
to 24 months to go from laboratory samples to marketable products" this
process, according to Cree's own graphs, is more like a decade from lab
to shop product.

By that reckoning, we might see such 300LPW LEDs by 2024 or shortly
thereafter. However, more realistically, we might see 160LPW lamps in
just another year or two which should produce a "drop in" LED replacement
for the 150W incandescent GLS lamp capable of lasting the promised 15 to
25 kilohours in all but the most poorly ventilated luminaires.

--
Johnny B Good